Shear plate and cutter assembly for rotary-type dry shaver



United States Patent SHEAR PLATE AND CU 1" E ER ASSEIVIBLY FOR RDTARY-TYPE DRY SHAVER John Brueeker, 1020 N. Verdugo Road, Glendale 6, Calif. Filed Dec. 2i), 1961, Ser. No. 160,855 2 Claims. (Cl. 30-43) The present invention relates generally to improvements in mechanical razors which are commonly referred to as dry shavers and are usually, but not necessarily, electrically-powered. The invention is specifically concerned with a particular shaving head which forms the operative part of a dry shaver and embodies a novel shear plate and a novel cooperating cutter.

Classified as to their basic mode of operation and with but few exceptions, electrically-powered dry shavers have, since their advent on the market, been of three types, namely, the oscillatory type, the reciprocating type, and the rotary type, these designations or appellations being based upon the kinds of motion which are imparted to the cutters. The present invention is concerned essentially or primarily with a dry shaver of the rotary type. As the designation suggests, in the rotary-type of dry shavers, the cutter has a cut-ting edge which sweeps in circumferential fashion around the inside face of a circular, conformably-shaped, shear plate.

In my co-pending United States patent application Serial No. 39,591, filed on June 29, 1960, which has matured into Patent No. 3,019,525, granted February 6, 1962, and entitled Shear Plate and Cutter Assembly for Rotary Type Dry Shaver, there has been disclosed a shaving head embodying a shear plate in which a lateral concavoconvex torus extends around the peripheral region of the otherwise fiat, circular plate. The torus is provided with a series of shear perforations therein and cooperate with a cutter element which has an arcuate cutting edge in contacting relation with the inner or inside face of the torus, and in connection with operation of the shaver, the torus in circumferential fashion. The advantages ascribed to such a shear plate and cutter combination are numerous and principal among these are an increased effective shearing area for a given diameter of shear plate and the presentation of two leading shearing areas of the torus to the skin of the user regardless of the direction of movement of the shear plate across the skin. The present invention is designed as an improvement over the shear plate and cutter assembly which is shown and described in my aforementioned copending patent application; and it has for an object thereof, the provision of a dry shaver which will promote or give a cleaner shave in less time than previously-designed dry shavers, including that of my copending application.

It is a further object of the invention to provide a dry shaver shear plate which has a lateral torus-like rib of V-shape cross-sectional configuration extending therearound and coacts with a cooperating cutter which is of commensurate or corresponding configuration and is adapted to sweep in circumferential fashion around the inside of the rib. By such an arrangement, the frustoconical faces of the annular rib of the V-shaft cross section will lie flat against the skin depression as the shear plate is moved across the face of the user and, consequently, present a more uniform pressure against the skin than is the case when a true torus of semi-circular cross-sectional configuration is employed in the plate.

Another object of the invention is to provide, in a dry shaver of the character under consideration, a shear plate and cooperating cutter assembly in which the shear plate is provided with two concentric torus-like ribs, each having associated therewith an individual cutter, and wherein the cutters are pressure-balanced, each against Blihdhii Patented Jan. 28, 1964 "ice the other, in a novel manner so that there will be no skipping by the cutters of the perforations in such ribs.

Another object of the invention is to provide, in connection with a dry shaver of the type under consideration, a novel and eifective means for reinforcing the central region of the shear plate so that, in use, the pressure of the plate against the skin will produce no flexing of the shear plate despite the relatively thin nature thereof.

A further object of the invention is to provide for use in connection with a dry shaver of the rotary type, a shear plate and cooperating cutter both of which readily lend themselves to economical manufacturing processes by simple stamping operations.

Numerous other objects and advantages of the invention, not at this time enumerated, will become apparent from a consideration of the following detailed description.

In the accompanying single sheet of drawing forming a part of this specification, one illustrative embodiment of the invention has been shown.

In this drawing:

FIG. 1 is a fragmentary sectional view taken substantially centrally and longitudinally through one form of shaving head constructed in accordance with the principles of the present invention;

FIG. 2 is a top plan view of the structure shown in FIG. 1 with a pontion of the shear plate broken away in order more clearly to reveal the nature of the cutters associated therewith;

FIG. 3 is a fragmentary side elevational view of one of the cutters and mounting means therefor;

FIG. 4 is an enlarged sectional view taken on the line 44 of FIG. 2;

FIG. 5 is a sectional View taken on the line 55 of FIG. 4; and

FIG. 6 is a front perspective view of one of the cutters employed in connection with the present invention.

Referring now to the drawings in detail, and in particular to FIG. 1, only those portions of a complete dry shaver which are necessary to an understanding of the present invention have been disclosed. The disclosed portions include a shaving head 10 and a fragmentary portion 12 of the shaver casing. The latter, as Well understood in the art, encloses an electric motor (not shown) by which the shaver as a whole is driven. The casing 12 is provided with an upstanding annular flange 14 which threadedly receives thereover the lower rim portion of the cylindrical side wall or shell 16 of the head. The upper circular rim 18 of the shell 16 is closed by a generally circular shear plate 20, the shape and design of which constitute one of the principal features of the present invention. The marginal region of the shear plate 20 is removably clamped to the rim 18 of the shell 16 by means of a clamping band 22 having an inturned clamping flange 24 which overlies a marginal seating flange 26 on the shell rim. Bayonet slot connections 28 serve to retain the band 22 removably in operative position on the shell 16.

The circular shear plate 24 is provided with a relatively large flat central hub portion 30 and a coplanar rim, this rim being the aforementioned seating flange 26. Between the flat central hub portion 30 and the seating flange 26, there are formed two concentric continuous circular ribs including an inner rib 32 and an outer rib 34. Such ribs are of V-shape cross-sectional configuration with the apex of each rib being presented upwardly as viewed in FIG. 1. The two ribs 32 and 34 are separated by a narrow circular fiat ring-like area 36 which lies in the plane of the central hub portion 30. Each rib is provided with an inner sloping frusto-conical side wall 37 and an outer sloping frusto-conical side wall 38 (see FIG. 4). The apex region or crest 39 between the two side walls 38 and 40 of each rib is rounded on a small radius. The ribs 32 and 34 are created by a lateral displacement of the metal of the shear plate in one direction and, therefore, they may be referred to as being of concavo-convex configuration despite the fact that they are not curved in radial cross section. Each rib 32 and 34 is formed with a series of shearing slots 46 (see FIGS. 2, 4 and these slots being equally and circumferentially spaced around the rib and each slot extending over and including the apex region of the rib. The slots are not truly radial in their direction of extent but extend at a slight angle to the radii which pass through their centers. Stated otherwise, each slot lies in a secant plane of major magnitude Each slot embraces the apex region of the rib in which it is formed and approximately one-half of each frusto-conical side region of the rib.

The shear plate 20 is adapted to cooperate with a series of three cutter assemblies 5!], each including two cutter elements proper, namely, an inner cutter element 52 designed for cooperation with the inner concavo-convex rib 32, and an outer cutter element 54 designed for cooperation with the outer concavo-convex rib 34. The cutter elements 52 and 54 of cutter assemblies 50 are balanced against each other and against the inside faces of their respective ribs 32 and 34 by reason of floating connections at the outer ends of a series of radial arms 56. The latter are formed on a hub 58 which is carried at the upper end of a drive shaft 60. The hub 58 is slotted as at 62 to receive a cross pin 64 by means of which the hub is driven from the drive shaft 60 while at the same time it has a limited degree of vertical sliding movement on the saft. A spring 66 bears at its lower end against a collar 68 which is secured as at 70 to the shaft 60. The upper end of the spring bears against the underneath end face 72 of the hub 58 with the result that the spring serves normally to urge the hub upwardly and thus maintain shearing pressure of the various cutter elements against the inside or concave faces of the ribs 32 and 34. The shaft 60 is adapted to be rotated in one direction by the aforementioned electric motor which is operatively mounted within the confines of the shaver casing 12.

Referring now to FIGS. 1 to 3, inclusive, the floating connections for the pairs of cutter elements 52 and 54 at the ends of the radial arms 56 include balance arms 80 which are pivoted medially of their ends by means of loose-fitting rivets 82 to upstanding flanges 84 (see FIG. 3) on the outer ends of the arms 56. Spacing washers 86 are interposed between the flanges 84 and the balance arms 80, and snap rings 88 are mounted on certain ends of the shanks of the rivets 82 and coact with the heads on the other ends of rivet shanks to hold the rivet against longitudinal displacement. The cutters 52 and 54 are pivotally connected by rivets 90 to the opposite end regions of the balance arms 80.

The cutters 52 and 54 are of identical design and construction and, therefore, a description of one of them will sufiice for the others. The cutters 52 and 54 may, if desired, be in the form of machined steel parts, but the design thereof is such that they readily lend themselves to a simple stamping operation. Each cutter (52 or 54, as the case may be) is in the form of a block-like body of tempered steel having a generally rectilinear edge configuration and possessing, specifically, eleven planar faces.

These faces appear variously in FIGS. 2 to 6 and include top thickness faces 92 and 94 which are disposed at an angle to each other. The angle is commensurate with the angle between the two sides 37 and 38 of the rib with which the cutter is associated with the result that the faces 92 and 94 normally lie flush with the inner or concave side of the rib. Each cutter also embodies narrow elongated vertically extending side thickness faces 96 and 98, a vertically extending front or leading face 100, a vertically extending rear or trailing face 162, an elongated narrow horizontally extending bottom thickness face 104, two forwardly and upwardly inclined leading faces 106 and 108 which extend at a wide angle to each other, and two similarly inclined trailing faces 110 and 112. The various faces of eachcutter are all rectangular in their configuration except for the side thickness faces 96 and 98 which may be described as being of dog leg design in that they are angular with the upper regions thereof being inclined forwardly and upwardly. The two top thickness faces 92 and 94 meet along an edge 114 which is slightly rounded so that there will be no binding of the apex of the cutter in the apex region 42 of the V- shaped rib within which the cutter operates and around which it sweeps in circumferential fashion.

As evidenced by the five thickness faces 92, 94, 96, 98 and 184, each cutter is possessed of appreciable thickness. However, in the interests of providing a simpler description of the irregular shape of the cutter, if the thickness thereof be disregarded and the cutter be regarded as formed from a blank of flat thin sheet metal, it could aptly be described as being comprised of a pentagon having two adjacent right angles and three adjacent obtuse angles, the sheet metal being bent forwardly in the region of the sides that define the central obtuse angle so that the sheet is cupped forwardly in this region.

As best shown in FIGS. 2, 4 and 6, the juncture lines and 122 between the top thickness faces 92 and 94 and the inclined leading faces 1% and 108 of the cutters constitute the actual operative shearing edges of the cutters, these edges cooperating with the edges of the shearing slots 46 to sever hairs when the shaver is in operation.

In order to reinforce the medial or central region of the generally circular shear plate 20 during use of the shaver, a fiat circular reinforcing plate is spot-welded as at 132 (see FIG. 1) to the central hub portion 30 and is substantially coextensive therewith. A thrust element 134 in the form of a rivet-like plug of nylon, Teflon or other similar wear resistant plastic material extends through aligned holes in the shear plate 20 and the reinforcing plate 130 and presents an inner downwardly facing flat thrust surface 136 for running contact with the upper rounded end 140 of the drive shaft 69. This thrust element 134 and the reinforcing plate 130 prevent inward flexing of the shear plate 20 when pressure is applied thereto during an actual shaving operation.

In the operation of the shaving head 10, rotation of the shaft 60 causes the hub 58, the radial arm 56 and the cutters 52 and 54 to turn bodily as a unit and also causes the cutters to sweep around the inside faces of the ribs 32 and 34, each cutter having the cutting edges thereof in intimate shearing contact with said inside faces of its res ective rib. The shearing edges of the cutters will encounter the opposed edges of the shearing slots 40 at a slight angle and thus the shearing action between these edges on the cutters and the ribs of the shear plate will be of an improved nature. Equal distribution of pressure or shearing force against the concave sides of the two torus-like ribs 32 and 34 will always be maintained by reason of the previously described balancing of the cutters 52 and 54 on opposite sides of the pivot points which are afforded by the rivets 82.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawing or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit of the invention. For example, while in the illustrated form of the invention, the shear plate 20 is shown as being provided with two continuous circular concentric concavo-convex ribs of V-shape cross section, it is within the scope of the invention to provide a greater number of such ribs if desired. For proper balancing of the individual cutters associated with such ribs, each pair of cutters Will be carried on a common balance arm and the balance arms will be arranged in pairs, each pair being carried on a common linking balance arm. Therefore,

only insofar as the invention has particularly been pointed out in the accompanying claims is the same to be limited.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

1. In a shearing head for a dry shaver of the rotary type, in combination, a generally circular shear plate provided with inner and outer concentric continuous annular lateral concave-convex ribs each having shearing slots therethrough, each rib presenting inner and outer side walls, an inner and an outer cutter movably mounted for circumferential sweeping movement around the inside concave surfaces of said inner and outer ribs respectively, and having elongated cutting edges in sweeping contact with the side walls of their respective ribs, a balance arm having its opposite end regions pivotally connected to the cutters, a drive shaft mounted for rotation about an axis coincident with the axis of said shear plate, a radial arm on said drive shaft, and means pivotally connecting the outer end of said arm to said balance arm between said cutters.

2. A dry shaver shearing head according to claim 1 and wherein said radial arm is provided with a sleeve-like hub at its proximate end, said hub being received over said drive shaft and slidable axially thereon, and a compression spring surrounding said drive shaft, having one end thereof bearing against a fixed reaction surface on the drive shaft, and having its other end bearing against said hub and serving normally to urge the latter yieldingly in the direction of said shear plate and thus seat the cutters against the side walls of their respective ribs.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN A SHEARING HEAD FOR A DRY SHAVER OF THE ROTARY TYPE, IN COMBINATION, A GENERALLY CIRCULAR SHEAR PLATE PROVIDED WITH INNER AND OUTER CONCENTRIC CONTINUOUS ANNULAR LATERAL CONCAVO-CONVEX RIBS EACH HAVING SHEARING SLOTS THERETHROUGH, EACH RIB PRESENTING INNER AND OUTER SIDE WALLS, AN INNER AND AN OUTER CUTTER MOVABLY MOUNTED FOR CIRCUMFERENTIAL SWEEPING MOVEMENT AROUND THE INSIDE CONCAVE SURFACES OF SAID INNER AND OUTER RIBS RESPECTIVELY, AND HAVING ELONGATED CUTTING EDGES IN SWEEPING CONTACT WITH THE SIDE WALLS OF THEIR RESPECTIVE RIBS, A BALANCE ARM HAVING ITS OPPOSITE END REGIONS PIVOTALLY CONNECTED TO THE CUTTERS, A DRIVE SHAFT MOUNTED FOR ROTATION ABOUT AN AXIS COINCIDENT WITH THE AXIS OF SAID SHEAR PLATE, A RADIAL ARM ON SAID DRIVE SHAFT, AND MEANS PIVOTALLY CONNECTING THE OUTER END OF SAID ARM TO SAID BALANCE ARM BETWEEN SAID CUTTERS. 